incorrect default value of boolean prop in defineProps

[CaiWenlie]

Vue version

3.5.13

Link to minimal reproduction

https://play.vuejs.org/#eNqFUstOwzAQ/JWVLwWpSg5wqtIiQD3AASrg6EuabIOLY1t+lEoh/87aoQ8kaG87O7P27NgduzUm2wRkE1a4ygrjwaEPBmSpmiln3nE240q0RlsP97o1sLK6hVGWRxBHR1xxVeTDNGkJeGyNLD0SAijSVE51kR8RbEyHV1qtRJOtnVbkoItyzirSC4n22XihFRmYQGIiV0qpPx9Tz9uA412/esfq44/+2m1jj7OFRYd2g5ztOV/aBv1Az1+fcEv1nmx1HSSpT5Av6LQM0eMguwuqJttHuuT2IWUnVPPm5luPyu2Wikajsk96zijLGNV/qx/sXmXXaY6rnlLcvcOZJ6SonQdjtXEwhRpXQuEioiLdUN5MwHlLNpObJUEV2iXaBCuCS60llirh+oDhC2jvdFxNhmYXl6d/Qy02qQDouh87PW1CTD5Qv39J/w0r/uD7

Steps to reproduce

define props like:

const props = defineProps<{
  a?: string,
  b?: number,
  c?: boolean,
  d?: boolean | undefined
}>()

got the result:

{ "c": false, "d": false }

What is expected?

default value of (not required) boolean props should be undefined

What is actually happening?

got false

System Info

No response

Any additional comments?

No response

[jacekkarczmarczyk]

It's not a bug, it's a documented behaviour https://vuejs.org/guide/components/props.html#boolean-casting